Aligned Allocation

[philip-paul-mueller]

While working on the nanobind interface my friend found an error related to gcc16 that is now a hard error.

The error is related to the following construct:

mid_deg = new double DACE_ALIGN(64)[2];

(dace/codegen/targets/cpu.py:492 and :541), where DACE_ALIGN(N) expands to __attribute__((aligned(N))) on GCC/Clang (dace/runtime/include/dace/types.h).

A small test program:

int main() {
    double *p = new double __attribute__((aligned(64)))[2];  // error on GCC 16
    delete[] p;
}

fails with the error:

test.cpp: In function »int main()«:
test.cpp:2:58: error: Ausrichtung der Arrayelemente ist größer als die Elementgröße
    2 |     double *p = new double __attribute__((aligned(64)))[2];  // error on GCC 16
      |                                                          ^

However, it only affects allocations of known small size.

According to my friend the annotation also does not have an effect.
If the alignment of the allocation should be controlled then std::align_val_t new expressions a C++17 feature must be used.